摘要
天然气水合物在海底沉积物中的饱和度是对其资源评价的重要参数.掌握水合物饱和度的影响因素对其能源和气候环境效应的评估有重要的意义.沉积物粒度属性与水合物饱和度的关系,几十年来仍停留在简单统计和定性认识层面.本研究以南海神狐SH3站位样品为研究对象进行粒度、比表面积的测量,以此为基础建立模型表征沉积孔隙大小、水合物相平衡改变量,探讨沉积物颗粒对天然气水合物饱和度的影响及其影响机理.实验结果显示,水合物产出于极细粉砂层(粉砂含量>60%).赋存水合物的地层含有极细砂以上的粗粒组分(<10%),而其上覆和下伏不含水合物的地层不含有这一粗粒组分.天然气水合物饱和度并非简单依赖于砂(>63mm)的含量,而与较粗的部分砂(>125mm)含量统计上存在更好的相关性.沉积颗粒的比表面积呈现较为平滑的走势,水合物产出层位的沉积物具有较小的比表面积(8~14 m^2/g),而不含水合物的层位其比表面积>16 m^2/g.孔隙度一定的前提下,沉积孔隙的大小主要由沉积颗粒的比表面积决定,且两者呈反比关系.沉积物颗粒的比表面积比其粒度更有优势,与水合物饱和度呈现良好的相关性,可用以定量化分析沉积孔隙大小、天然气水合物相平衡条件的改变,是研究沉积物颗粒影响天然气水合物分布有效且经济的参数指标,同时也还需要大量实验的验证或改进.
An important parameter is the saturation of gas hydrate within the sediment pore for evaluating its impact on energy, climate and environment. So it is significant of understanding which factors affecting the saturation of gas hydrates. There is a good relationship between the gas hdyrate saturation and the sediment granulometric charateristics by previous investigations. Gas hydrates with high saturation are retrieved usually from the turbidite, sand layers, which formations are of coarse particles and relatively larger pore space. But the knowledge up to today is still on the level of simple statistic and qualitative. In this paper, the samples from site SH3, Shenhu, South China Sea, are undergone the grain size ＆ specific surface area （SSA） measurements. Then a mathematical model is built to depict that the SSA characterizing the pore size and the change of gas hydrates phase equilibruim condition. Thus, the scientific question, how the sediment grains affecting the gas hydrates saturation, can be analysed and discussed quantitatively. The experiment results show that, the sediment layers which are not bearing gas hydrates, consist of clay（〈4 ~tm）, silt （4-63 μm） and the very fine sand （63-125 μm）. The major components of silt （4-63 μm） contribute to 80%, while the content of clay is almost 20%. The gas hydrate occurrence zone （GHOZ） is constrained by the fine silt layers （silt content〉60%）. The sediment layer of GHOZ contains the most coarsest grains （〉125 μm, content〈10%） of sand except for the very fine sand （63-125μm）, while the layers up ＆ below GHOZ do not contain the coarsest parts. The gas hydrate saturation does not depend simply on the sand （〉63 μm） content. There is a more better correlation between hydrate saturation and the sand content except for the very fine sand （〉125 μm）. This is by now the most elaborate report of the relationship between gas hydrates saturation and sediment grain size characterization. The SSA of sediment gr
出处
《科学通报》
EI
CAS
CSCD
北大核心
2016年第3期388-397,共10页
Chinese Science Bulletin
基金
中国科学院重点部署项目(KGZD-EW-301)
中国科学院国家外国专家局创新团队国际合作伙伴计划
中国科学院广州能源研究所所长基金(y007r51001)资助
中国地质调查局地质调查项目(GHZ2012006003)
广东省博士启动项目(S2013040013738)
关键词
天然气水合物饱和度
沉积物粒度
比表面积
南海
gas hydrate saturation, sediment grain size （sediment granulometric distribution）, specific surface area （SSA）,South China Sea
